1. Field of the Invention
The present invention relates to a method for producing a liquid ejecting head for ejecting a desired liquid by generation of a bubble with application of thermal energy to the liquid. More particularly, the invention relates to a method for producing a liquid ejecting head using a movable member which is constructed so as to be displaced in response to the generation of a bubble. Further, the present invention concerns a liquid ejecting head, a head cartridge using the liquid ejecting head, a liquid ejecting apparatus, and a head kit.
The present invention is applicable to equipment such as a printer, a copying machine, a facsimile machine having a communication system, a word processor having a printer portion or the like, and an industrial recording device combined with various processing device or processing devices, in which the recording is effected on a recording material such as paper, thread, fiber, textile, leather, metal, plastic resin material, glass, wood, ceramic and so on.
In this specification, "recording" means not only forming an image of letter, figure or the like having specific meanings, but also includes forming an image of a pattern not having a specific meaning.
2. Related Background Art
An ink jet recording method of so-called bubble jet type is known in which an instantaneous state change resulting in an instantaneous volume change (bubble generation) is caused by application of energy such as heat to the ink, so as to eject the ink through the ejection outlet by the force resulted from the state change by which the ink is ejected to and deposited on the recording material to form an image formation. As disclosed in U.S. Pat. No. 4,723,129, a recording device using the bubble jet recording method generally comprises an ejection outlet for ejecting the ink, an ink flow path in fluid communication with the ejection outlet, and an electrothermal transducer as energy generating means disposed in the ink flow path.
With such a recording method is advantageous in that, a high quality image, can be recorded at high speed and with low noise, and a plurality of such ejection outlets can be located at high density, and therefore, small size recording apparatus capable of providing a high resolution can be provided, and color images can be easily formed. Therefore, the bubble jet recording method is now widely used in printers, copying machines, facsimile machines or another office equipment, and for industrial systems such as textile printing device or the like.
For such a bubble jet recording method, a proposal was made to employ a structure incorporating a movable member such as a valve or the like in a flow path in order to improve the ejection efficiency.
For example, Japanese Laid-Open Patent Application No. 63-199972 describes a method for producing valve elements in an ink jet recording head with valves in flow paths.
In this publication patterns of the valves are formed by photolithography of a photosensitive resin or the like.
Further, Japanese Laid-Open Patent Application No. 63-197652 describes a method for producing valves in an ink jet recording head with check valves provided on the upstream side of the flow paths.
In this publication, the valves are integrally formed with a substrate, utilizing parts of the substrate, by photolithography.
Japanese Laid-Open Patent Application No. 6-31918 (U.S. Pat. No. 5,278,585) discloses a method for producing an ink jet head having one-way valves. This is the method for producing the ink jet head having a silicon substrate and movable members patterned by photolithography and processed by anisotropic etching. This publication also discloses a method for forming the movable members of a silicon dioxide layer in the silicon substrate, a method for forming the movable members in a surface region of a silicon wafer by implantation or diffusion of boron, a method for forming the movable members by patterned etching stop occurring because of implantation of boron, and so on.
As the background art of the present invention there was a background art subject to enhance the fundamental ejection characteristics up to a conventionally unexpected level, from a conventionally inconceivable standpoint, in the basically conventional method for ejecting the liquid by forming a bubble (particularly, a bubble formed by film boiling) in a liquid flow path.
With this background art subject, some of the present inventors came to find that the most significant factor to considerably improve the ejection characteristics was to take account of a growing component downstream of the bubble, based on the consideration of influence of energy given by the bubble per se on an ejection amount. Namely, it was found that the ejection efficiency and ejection speed could be improved by efficiently directing the component downstream of bubble into a direction of ejection. Based on this finding, the inventors came to an extremely high technical level, when compared with the conventional technical level, to positively move the downstream component of bubble to the free end side of the movable member.
Further, it was also found that it was preferred to take account of structural elements such as the movable member and liquid flow path related to growth of bubble on the downstream side in a heating region for forming the bubble, for example, on the downstream side from the center line passing the center of the area of an electrothermal transducer in the direction of flow of liquid, or at the center of the area of a surface contributing to bubble generation.
Based on the above findings, some of the present inventors invented and already proposed a liquid jet head of an utterly novel structure.
This head has a first path portion in fluid communication with an ejection outlet, a second path portion with an electrothermal transducer provided therein, and a partition wall disposed between the first path portion and the second path portion and having a movable member arranged as displaceable to the first path portion side, in which the first path portion becomes in fluid communication with the second path portion when the movable member is displaced.
This head is arranged to effect ejection in such a way that a bubble is generated through drive of the electrothermal transducer, the movable member comes to be displaced to the first path portion side with growth of the bubble, and the pressure thereof is guided toward the ejection outlet by the movable member displaced.
In the liquid ejecting head using the movable member displaced depending upon the bubble as described above, the head is produced by positioning, jointing and securing through a press (stop) spring a substrate having the electrothermal transducer, side walls of the second path portion, the partition wall having the movable member, a grooved top plate having side walls of the first path portion.
In the above method for producing the liquid ejecting head, a gap, however, may sometimes occur between the partition wall and the second path portion walls because of variations in production. This is not easily checked depending on manufacture control. If the space appeared in this region the pressure for discharging the bubble might escape through this gap so as to cause ejection failure due to insufficient ejection pressure. Since the pressure wave escaping through the gap propagated into adjacent flow paths and fluctuated the liquid therein, variations of ejection amounts might sometimes occur upon continuous drive. A conceivable means for avoiding the occurrence of the gap is to bond the partition wall with the second path portion walls with an adhesive, but it is not preferred because in that case the adhesive could intrude into the space between the movable member and the partition wall so as to disable movement of the movable member.
Further, the above producing method needs positioning among the substrate, the partition wall, and the grooved top plate, so that it takes a lot of time for securing the positioning accuracy.